The present invention relates to a composite material having dispersed therein an active organic compound, as well as to an effluent treatment process, especially a photographic effluent treatment process.
Many manufacturing and processing methods generate effluents which, on the one hand, cannot be directly disposed of via the sewers because of their composition and, on the other hand, contain substances the recovery and re-use of which would be economically gainful. One example is the photographic processing industry, in which exposed silver halide photographic films and papers are treated in successive processing baths that are rich in chemicals. Such photographic film processing methods are well known (see for example, Chimie et Physique Photographiques; Pierre Glafkides, Vol. 2, Chap XL, pages 947-967).
In general, photographic processing comprises several processing baths and one or more wash and/or stabilization baths. The build-up in the wash and/or stabilization baths of substances carried over from the preceding processing steps is especially detrimental not only to the stability of developed photographic images and to the good keeping of sensitometric characteristics, but also to the possibility of recycling these wash and stabilization baths, or discharging them to the sewers. After processing, the wash and stabilization baths are found to contain inorganic compounds, such as iron, silver, thiosulfate, and sulfate ions, or organic compounds which are, either substances used for development, or products coming from the reaction of these substances during development, or from the step of fixing or bleach-fixing.
The problem of discharging silver to the sewers is especially important because of new standards that apply to photographic processing methods. There are notably standards that set the maximum volume of water that should be used for washing 1 m2 of photographic material. In particular, for processing radiographs, the current French standard permits the use of 15 liters of water per m2 of single-coated radiographic product to be processed and 30 liters of water per m2 of double-coated radiographic product, with discharge to the sewers of water containing a maximum of 1 ppm of silver. Reducing the permissible volume of water produces wash baths that are more concentrated in silver and thus more difficult to decontaminate.
In addition, during the use of the baths, there is a biological growth, especially in the prebaths, the stabilization baths and the wash baths. If it is not controlled the growth of microorganisms causes the formation of sludge that can clog up the installation, deteriorate the process bath, and thus lead to a defective quality of the photographic image. Problems related to the growth of microorganisms are increasingly critical as the quantities of water permitted for processing photographic materials are increasingly restricted.
The use of biocides to prevent or limit biological growth in processing solutions is a current practice. For greater safety, quantities are used in excess of the strictly necessary amount. In this case, the water discharged into the environment contains large amounts of biocides, which create problems for treatment plants that use microorganism activity for treating effluents.
Therefore it would be desirable to provide a new process which can reduce the quantity of silver in ionic form contained in the photographic effluent and which can deliver a controlled amount of active organic compound, such as a biocide, in the effluent. It is also useful to have a process that is easy to apply and economic.
This objective is achieved with a composite material which comprises an aluminosilicate organic-inorganic polymer matrix in fiber form comprising at least on the surface an organic radical having a xe2x80x94SH or xe2x80x94S(xe2x80x94CH2)nxe2x80x94Sxe2x80x94 function with n between 0 and 4 and in which an active organic compound is dispersed.
The present invention further relates to a process for obtaining such a composite material. This process comprises the hydrolysis in a basic medium of an alkylalkoxysilane of the formula RSiR1x(OR2)3xe2x88x92x in which R is an alkyl group having a xe2x80x94SH or xe2x80x94S(xe2x80x94CH2)nxe2x80x94Sxe2x80x94 function with n between 0 and 4, R1 and R2 are independently a methyl or ethyl group, x is 0 or 1, in the presence of an active organic compound and an aqueous solution of an aluminosilicate inorganic polymer in fiber form comprising active hydroxyl groups on the surface. xe2x80x9cActive hydroxyl groupsxe2x80x9d are groups capable of reacting with alkylalkoxysilane in an aqueous medium.
Finally the present invention relates to a treatment process for photographic effluents containing silver in ionic form, as well as a device for carrying out this process. The treatment process of the invention comprises contacting the composite material with the effluent.
The process of the present invention is especially efficient for treating photographic baths used for processing silver halide photographic materials. For photographic baths, the silver is in the form of an ionic complex.
The treatment process of the invention does not modify the properties of the effluent treated. In particular, the pH of the effluent before and after the invention treatment as well as the salt content of the effluent stay unchanged. In addition, the nature of the water making up the effluent to be treated does not modify the efficiency of the treatment.
In the scope of the invention, it is not worthwhile previously diluting the treated effluent.
The composite material according to the invention has the advantage of being photographically inert, so that there is no detrimental effect on the sensitometric characteristics of the final images.